Study of Mid-Infrared Emission and Structural Properties of Heavy Metal Oxide Glass and Optical Fibre Co-Doped with Ho3+/Yb3+ Ions

Bismuth-germanate glasses with low hydroxide content co-doped with Ho3+/Yb3+ ions have been investigated in terms of structural and spectroscopic properties. To reduce OH- ions content and improve transmittance value at the wavelength of 3.1 &micro
m, the glass synthesis has been carried out in low vacuum conditions (45&ndash
65 mBar). The composition of the host glass based on heavy metal oxides affects the maximum phonon energy (h&omega
max = 724 cm&minus
1), which low value has a positive impact on the mid-infrared emission parameters. Emission band at the wavelength of 2.87 &micro
m was observed in glass co-doped with mol% 0.25 Ho2O3/0.75 Yb2O3 under 980 nm high power laser diode wavelength excitation. Lifetime measurements of the Yb3+:2F5/2 quantum level indicate efficient Yb3+ &rarr
Ho3+ energy transfer (&eta
= 61%). The developed active bismuth-germanate glass was used as the core of optical fibre operating in the mid-infrared region.